Roller hysteresis clutch



April 20, 1965 D. H.- BURNS ROLLER HYSTERESIS CLUTCH 2 Sheets-Sheet l Filed June 29, 1961 April 20, 1965 D. H. BURNS ROLLER HYSTERESIS CLUTCH 2 Sheets-Sheet 2 Filed June 29, 1961 Tim INVENTOR. AV/ 9M/vf fvwm/Kif United States Patent C 3,179,218 ROLLER HYSTERESS CLUTCH David. H. Burns, Los Angeles, Calif., assigner to Talento graph Corporation, Los Angeles, Calif., a corporation of Virginia Filed .lune 29, 19161, Ser. No. 120,663 l Claim. (Cl. @QL-21.5)

This invention relates to torque transfer devices and more particularly to an improved electrically controlled clutch employing hysteresis effects.

In many electromechanical systems it is desired to accurately control the movement of mechanical members inresponse to electrical signals. One device for providing such controlled movement is an electrically controllable clutch. Generally, such clutches provide a slipping friction Contact between clutch elements, the degree of slippage therebetween being controllable by the magnitude of the current signal applied to the clutch. Such clutches, to provide a torque transfer which is substantially proportional to the current signal applied thereto, however, generally require close tolerances between the clutch elements. Further, due to the friction Contact between the clutch elements, these clutches require a relatively rugged design utilizing physically hard elements which may be diicult to machine.

ln View of this, the present invention provides an electrically controllable clutch wherein the tolerances between clutch elements are not critical. The clutch provides a substantially proportional torque output and utilizes relatively soft materials which are easily machined.

To accomplish this, the present invention provides a clutch employing hysteresis effects to provide a torque transfer between clutch elements which is substantially proportional to the magnitude of a current signal applied to the clutch.

More particularly, a basic form of the present invention includes first and second clutch elements of soft magnetic material which are mounted for relative movement about their axes of rotation. Disposed between the clutch elements and maintaining continuous contact therewith are a `plurality of roller bearings of hard magnetic material having a high flux remanence. Accordingly, the clutch elements are normally free to rotate relative to each other with a minimum of friction.

To produce the desired torque transfer between the clutch elements, means are included within one of the clutch elements for generatinor a magnetic field proportional to the current applied thereto. ln particular, the magneticeld magnetizes one of the clutch elements to a north magnetic pole and the other clutch element to a south magnetic pole. Thus, as one of the clutch elements rotates relative to the other, the roller bearings are caused to roll over a clutch element through the magnetic eld. In so doing, the magnetic material of each roller bearing is forced through its hysteresis loop such that a force, which may be termed a hysteresis force, is set up on the rst and second clutch elements opposing the movement of the moving clutch element and tending to cause the other clutch element to rotate with the moving clutch element. This hysteresis force is proportional to the area of the hysteresis loop of the magnetically hard material. By varying the magnitude of the current signal to increase the magnetizing force, the magnitude of the hysteresis force-is increased up to saturation of the roller bearings. ln particular, it has been found that the torque transfer between clutch elements increases in a substantially proportional manner with the magnitude of the current applied to the clutch.

Accordingly, the present invention, by providing a con-V tinuous roller hearing Contact between clutch elements does not require the critical close tolerances between 3, l @di ld Patented Apr. 20, 1965 ICC clutch elements of the prior art, and hy utilizing magnetically soft material for the clutch elements, which are generally `also physically soft, the present invention provides a clutch design which may be readily machined.

For a more complete understanding of the present invention, reference should be made to the following detailed description when considered with the drawings, in which:

FiGURES l and 2 are diagrammatic representations of an embodiment of the clutch utilizing the hysteresis design of the present invention; and

FlGURES 3 and 4 are diagrammatic representations of another embodiment of the present invention.

As represented in FIGURES l and 2, the present invention includes first and second clutch elements of soft magnetic material mounted for relative movement about their axes of rotation. ln particular, the iirst clutch element includes a drum lil pinned at l2 for movement :ith a shaft ld. Further, as shown, the drum lll includes an annular slot lo around the periphery of the drum lll.

As illustrated in FIGURE l, the second clutch element of the present invention includes a hollow cylinder 18 of soit magnetic material which is radially disposed for rotation around the drum lll. To provide substantially free rotation between the clutch elements, a iirst and second plurality of cylindrical roller bearings represented at 2li and 22, respectively, are disposed around the periphery of the drum lll on either side of the slot le. These roller bearings, as illustrated, maintain continuous rolling Contact with the cylinder lid and the drum ld.

To prevent lateral movement of the cylinder l, the present invention, as represented in FIG-URE 1, includes two retaining disks 2d and 26, respectively. As represented, the retaining disks 2d and 2d are coupled to the drum lil for rotation therewith. To provide a substantially friction-free contact between the retainers 24 and 26 and the cylinder i8, the present invention includes a plurality of hall bearings, four of which are represented at 2li, Sil, 32, and 3ft, respectively. Accordingly, the drum lil and the cylinder i3 are free to rotate relative to each other with a minimum or friction. To provide rotational movement for the cylinder i3, the` cylinder i3 includes a toothed Wheel, represented at` 36, which is driven by a second toothed wheel represented at 33. Accordingly, in the embodiment of the present invention as represented in FIGURES l and 2, it is desired to transfer torque from the moving cylinder 18 to the drum lill, the torque output being taken from the shaft 14,

To provide the desired clutch action of the present invention, a coil hob'oin assembly, represented at 4d, is included within the annular slot lo. In particular, a current signal applied over the coil leads, represented at 42, to the coil bobbin assembly Lili generates a magnetic field, the linx path of which is represented by the broken p line lid. Thus, as illustrated, a magnetic field having a flux path is setup which passes from the drum lll radially across the roller bearings 2t) longitudinally along the cylinder l, radially through the roller bearings `22, to the drum lll. f

ln operation, as the cylinder 18 is rotated relative to the drum lil, the roller bearings Ztl and 22 are caused to roll over the periphery ofthe drum lll. ln so doing, the roller bearings pass through the magnetic field set up hy the coil bobbin assembly. As the roller bearings rotate, the magnitude of the magnetizing force relative to a given physical cross-sectional axis of the roller bearings varies. With the roller bearing Ztl in the position as shownin FGURE 2, the magnetizing force acting uponthe crosssectional axis aligned with the magnetizing torce repre sented hy the arrow lo is maximum. However, as the roller bearing Ztl rotates ninety degrees (90), the magnia tude of the magnetizing force acting on the given crosssectional axis decreases to zero, while, when the roller bearing 2t) has rotated one hundred and eighty degrees (180), the magnetizing force relative to the physical cross-sectional axis is again of maximum magnitude but of opposite polarity. Thus, as the roller bearing 2t? rolls through three hundred and sixty degrees (360), it is forced through its inherent hysteresis loop.

As is commonly known, to force a magnetic material through its hysteresis loop requires a finite amount of energy which is proportional to the area enclosed by the hysteresis loop. In the case of the present invention, the energy required to rotate a roller bearing, such as 20, through three hundred and sixty degrees (360) sets up a force termed the hysteresis force opposing this movement. In particular, the hysteresis force of each roller bearing acts on the drum and the cylinder 18 to oppose any relative movement between the cylinder 1S and the drum 10, causing the drum l0 to rotate with the cylinder i8. Accordingly, as the cylinder 18 is rotated relative to the drum lt) torque is transferred to the drum 16.

To vary the torque transferred from the cylinder 1S to the drum 1t?, the magnitude of the current applied to the coil bobbin assembly is varied. As the magnitude of the current signal is increased, the magnetizing torce is likewise increased. ln turn, as the magnetizing force acting on the roller bearings increases, the area of the hysteresis loop for the hard magnetic material increases, thereby increasing the magnitude of the hysteresis force. In practice it has been found that so long as the magnetizing force is not great enough to saturate the roller bearings 2) and 22, the torque applied to the drum 1t) increases substantially in direct proportion to the magnitude of the current applied to the coil bobbin assembly 453.

Although the above description has described a clutchV utilizing hysteresis etects, it is to be understood that if the drum llt) were stationary and a magnetic ield set up as described above, the device shown in FIGURES 1 and 2 would embody a hysteresis brake tending to retard and stop the motion of the cylinder i8.

Referring to FIGURES 3 and 4, there is shown in schematic form another embodiment of the present invention. As illustrated, this embodiment of the invention includes first and second clutch elements of soft magnetic material mounted for relative movement abount their axes of rotation. As shown, the first clutch element includes a drum 48 which is pinned to a shaft 5@ for rotation therewith. Further, disposed within the drum 48 is an annular slot 52. As shown, the annular slot 52 divides a radial surface of the drum 48 into inner and outer planar surfaces 54 and 56, respectively. As shown, the inner planar surface 54 projects beyond the plane of the outer planar surface 56. Further, the outer planar surface 56 is tapered radially away from the plane of the inner planar surface 54.

As illustrated in FTGURE 3, the second clutch element includes a disk 58 of soft magnetic material. As represented, the disk 5S is mounted for free rotation around the shaft 50. By way of example only, the disk 5S comprises a toothed gear wheel which, in conjunction with a gear wheel, a portion of which is represented at 60, is caused to move relative to the drum 43. As is further represented in FIGURE 3, the disk SS has an inner surface that includes the circular portion represented at 62 and is tapered radially away from the plane of the inner planar surface of the drum 4d.

To provide for a substantially friction-free rotation between the disk 58 and the drum 48, the present invention as illustrated in FlGURES 3 and 4, includes a cage 64 of non-magnetic material disposed between the drum ZSand the disk 53. As represented, the cage 64 is disposed around the periphery of the inner planar surface 54 and includesV a plurality of radial slots 66 that are radially tapered toward the center of the shaft 50.

As represented in FGURE 3, to provide a continuous low friction contact between the drum 43 and the disk 58, a plurality of tapered needle roller bearings are ineluded. in particular, a bearing 68 is disposed in each of the radial slots 66 and maintains continuous rolling contact between the outer planar surface 56 and the tapered portion 62 of the disk 58. Accordingly, the disk 58 is free to rotate with low friction relative to the drum 43 by movement of the gear wheel 6i).

To provide the desired clutch action of the present invention, a coil bobbin assembly, represented generally at 7d, is included within the annular slot 52.

ln operation, in providing the clutch action of the present invention, as the disk 5S is rotated a current signal is applied to the leads '74 which energizes the coil represented at 76 to generate a magnetic field having a lux path denoted by the dotted line 7S. Thus, upon energization of the coil bobbin assembly 7G, a magnetic eld is set up having a ilux path which passes from the drum d8 radially through the roller bearings 68, radially through the disk 5?, returning to the drum 48. Thus, as the disk 5S rotates relative to the drum 48, the roller bearings 68 are caused to roll over the outer planar surface 56 through the magnetic eld. As previously described, this produces a hysteresis force which acts upon the disk 58 and the drum 4S in opposition to the movement of the disk 58 and tending to cause the drum 48 to rotate with the disk 58. In particular, it has been found in practice that the torque transfer to the drum 48 is substantially proportional to the magnitude of the current applied to the coil bobbin assembly 7 t?.

As in the embodiment described in connection with FIGURES 1 and 2, the embodiment shown in FIGURES 3 and 4 may produce a braking action. If the drum 48 is stationary, application of a current signal to the coil bobbin assembly 7@ produces a hysteresis force acting upon the disk S8 to tend to reduce the movement of the disk 58.

What is claimed is:

A roller hysteresis clutch comprising: a drum of soft magnetic material having an annular slot centrally disposed along its longitudinal axis, said drum being mounted for movement about its axis of rotation; a first plurality or' needle-like roller bearings disposed around the periphery of said drum adjacent to one side of said annular slot, said roller bearings being composed of a magnetic material having a high ux remanence; a second plurality of needle-like roller bearings disposed around the periphery of said drum adjacent to another side of said annular slot, said roller bearings being composed of a magnetic material having a high flux remanence; an annular shroud of soft magnetic material disposed for rotation around said drum in continuous contact with said first and second plurality of roller bearings; a coil bobbin assembly disposed within said annular slot for generating a magnetic iield having a ux path which extends from said drum radially outwardly from the axis of rotation of the drum through said rst plurality of roller bearings into the annular shroud, longitudinally through said annular shroud, radially inwardly toward the axis of rotation of the drum through said second plurality of roller bearings to said drum; and means for rotating said annular shroud around said drum to cause said first and second plurality of roller bearings to roll on the periphery of said drum through said magnetic Iield to produce a hysteresis force upon said drum causing it to rotate with said annular shroud.

References Cited hy the Examiner UNITED STATES PATENTS 1,334,759 5/20 Huebner 192-40 2,596,654 5/52 Clark et al. 308-183 X 2,718,292 9/55 Meilander et al. 192-40 3,034,365 5/62 Stieber 192-30 X DAVID J. WILLIAMOWSKY, Primary Examiner.

THOMAS I. HTCKEY. Examiner. 

